Semiconductor device

ABSTRACT

A semiconductor device includes: a first gate structure on a substrate; a first drain region having a first conductive type adjacent to one side of the first gate structure; a source region having the first conductive type adjacent to another side of the first gate structure; and a first body implant region having a second conductive type under part of the first gate structure.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a semiconductor device, and more particularly to a lateral-diffusion metal-oxide semiconductor (LDMOS) device.

2. Description of the Prior Art

In current semiconductor processing, controllers, memories, circuits of low-voltage operation and power devices of high-voltage operation are largely integrated into a single chip to achieve a single-chip system. The power device, such as vertical double-diffusion metal-oxide-semiconductor (VDMOS), insulated gate bipolar transistor (IGBT) and lateral diffusion MOS (LDMOS), is employed to increase power switching efficiency and decrease the loss of energy resources. It is often required that the switching transistors withstand high breakdown voltages and operate at a low on-resistance.

However in today's high voltage devices, the gate pattern of the LDMOS typically has a T-shape or H-shape cross-section which usually has higher resistance under the gate structure. Hence how to improve the design of current high voltage device so that the device would have higher performance has become an important task in this field.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a semiconductor device includes: a first gate structure on a substrate; a first drain region having a first conductive type adjacent to one side of the first gate structure; a source region having the first conductive type adjacent to another side of the first gate structure; and a first body implant region having a second conductive type under part of the first gate structure.

According to another aspect of the present invention, a semiconductor device includes: a first gate structure extending along a first direction on a substrate; a first drain region extending along the first direction on one side of the first gate structure; a first source region adjacent to another side of the first gate structure; and a first body implant region extending along the first direction and overlapping part of the first gate structure.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a top view of a LDMOS device according to an embodiment of the present invention.

FIG. 2 illustrates a cross-section view of the LDMOS device along the sectional line AA′.

FIG. 3 illustrates a cross-section view of the LDMOS along the sectional line BB′.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, FIGS. 1-3 illustrate structural views of a LDMOS device according to an embodiment of the present invention, in which FIG. 1 illustrates a top view of the LDMOS device, FIG. 2 illustrates a cross-section view of the LDMOS device along the sectional line AA′, and FIG. 3 illustrates a cross-section view of the LDMOS along the sectional line BB′.

As shown in FIG. 1, the semiconductor device includes a first gate structure 14 and a second gate structure 16 extending along a first direction (such as Y-direction) on a substrate 12, a gate pattern 18 extending along a second direction (such as X-direction) to connect the first gate structure 14 and the second gate structure 16, a first drain region 20 extending along the first direction on one side of the first gate structure 14, a first body implant region 22 extending along the first direction and overlapping part of the first gate structure 14, a second drain region 24 extending along the first direction adjacent to one side of the second gate structure 16, and a second body implant region 26 extending along the first direction and overlapping part of the second gate structure 16.

The semiconductor device further includes a first source region 28 disposed on another side of the first gate structure 14 or between the first gate structure 14 and the second gate structure 16, a second source region 30 disposed above the first source region 28, a third source region 32 disposed below the first source region 28, a first body contact region 34 extending along the second direction between the first source region 28 and the second source region 30, a second body contact region 36 extending along the second direction between the first source region 28 and the third source region 32, and a plurality of contact plugs 38 electrically connecting the gate pattern 18, the first drain region 20, the second drain region 24, the first source region 28, the second source region 30, and the third source region 32.

Viewing from a more detailed perspective, an edge of the first body implant region 22 is aligned with an edge of the first gate structure 14, an edge of the second body implant region 26 is aligned with an edge of the second gate structure 16, and the left sidewall and right sidewall of the first body contact region 34 overlap part of the first gate structure 14 and part of the second gate structure 16 respectively, align with the edges of the first body implant region 22 and the second body implant region 26, and separate the first source region 28 and the second source region 30 so that the two regions 28, 30 not overlapping each other. Similarly, the left sidewall and right sidewall of the second body contact region 36 overlap part of the first gate structure 14 and part of the second gate structure 16 respectively, align with edges of the first body implant region 22 and second body implant region 26, and separate the first source region 28 and the third source region 32 so that the two regions 28, 32 not overlapping each other.

Referring to FIGS. 2-3, in which FIGS. 2 illustrates a cross-section of FIG. 1 along the sectional line AA′ and FIG. 3 illustrates a cross-section of FIG. 1 along the sectional line BB′. As shown in FIGS. 2-3, the semiconductor device when viewed from another perspective includes a shallow trench isolation (STI) 40 disposed in the substrate, a first gate structure 14 and second gate structure 16 disposed on the substrate 12 between the STI 40, a first drain region 20 disposed adjacent to one side of the first gate structure 14, a first drift region 42 disposed under part of the first gate structure 14 and part of the salicide block (SAB) 56 and extended to and contacting the first drain region 20, a first source region 28 disposed on another side of the first gate structure 14 or in the substrate 12 between the first gate structure 14 and the second gate structure 16, a first body contact region 22 under part of the first gate structure 14, a second drain region 24 disposed adjacent one side of the second gate structure 16, a second drift region 44 disposed under part of the second gate structure 16 and part of the of the salicide block 56 and extended to and contacting the second drain region 24, and a second body contact region 26 under part of the second gate structure 16.

In this embodiment, the substrate 12 preferably includes a silicon-on-insulator (SOI) substrate, which could further includes a first semiconductor layer 46, an insulating layer 48 disposed on the first semiconductor layer 46, and a second semiconductor layer 50 disposed on the insulating layer 48. Preferably, the first semiconductor layer 46 and the second semiconductor layer 50 could be made of semiconductor material including but not limited to for example silicon, germanium, or silicon germanium (SiGe) and the insulating layer 48 could be made of dielectric material including but not limited to for example silicon oxide.

It should be noted that since the device disclosed in this embodiment pertains to a n-type LDMOS device, elements including the first drain region 20, the first drift region 42, the first source region 28, the second drain region 24, and the second drift region 44 preferably include a first conductive type such as n-type, whereas the elements including the first body contact region 34, the second body contact region 36, the first body implant region 22, and the second body implant region 26 preferably include a second conductive type such as p-type. Nevertheless, according to other embodiments of the present invention it would also be desirable to employ the same architecture disclosed in this embodiment to a p-type LDMOS device and in such instance the first drain region 20, the first drift region 42, the first source region 28, the second drain region 24, and the second drift region 44 would preferably include a first conductive type such as p-type while elements including the first body contact region 34, the second body contact region 36, the first body implant region 22, and the second body implant region 26 would include a second conductive type such as n-type, which is also within the scope of the present invention.

In this embodiment, the first source region 28, the first drain region 20, and the second drain region 24 preferably share same concentration, the first drift region 42 and the second drift region 44 preferably have same concentration, and the concentration of the first source region 28, the first drain region 20, and the second drain region 24 is preferably greater than the concentration of the first drift region 42 and the second drift region 44. The first body contact region 34 and the second body contact region 36 preferably have same concentration, the first body implant region 22 and the second body implant region 26 preferably have same concentration, and the concentration of the first body contact region 34 and second body contact region 36 is preferably greater than the concentration of the first body implant region 22 and the second body implant region 26.

Preferably, the STI 40 and all of the doped regions including the first drain region 20 on the left to the second drain region 24 on the right are all disposed within the second semiconductor layer 50 of the substrate 12 and the bottom surfaces of the STI 40 and all of the doped regions are even with the bottom surface of the second semiconductor layer 50. Even though an edge of the first body implant region 22 is aligned with an edge of the first gate structure 14 as shown in FIG. 2 while an edge of the second body implant region 26 is also aligned with an edge of the second gate structure 16, according to other embodiments of the present invention, the edge of each of the body implant regions could also be not aligned to the edge of each of the gate structures.

For instance, the right edge or right sidewall of the first body implant region 22 could be not aligned to an edge of the first gate structure 14 such that both the left and right edges of the first body implant region 22 could be directly under the first gate structure 14 at the same time, or the right edge of the first body implant region 22 could be slightly extended to the right and passing the edge of the first gate structure 14. Similarly, the left or left sidewall of the second body implant region 26 could be not aligned to an edge of the second gate structure 16 such that both the left and right edges of the second body implant region 26 could be directly under the second gate structure 16 at the same time, or the left edge of the second body implant region 26 could be slightly extended to the left and over the edge of the second gate structure 16, which are all within the scope of the present invention.

In this embodiment, the formation of each of the gate structures including the first gate structure 14, the second gate structure 16, and the gate pattern 18 connecting the first gate structure 14 and the second gate structure 16 could be accomplished by a gate first process, a high-k first approach from gate last process, or a high-k last approach from gate last process. Since this embodiment pertains to a gate first approach, a gate dielectric layer 52 or interfacial layer, a gate material layer 54 made of polysilicon, and a selective hard mask could be formed sequentially on the substrate 12, and a photo-etching process is then conducted by using a patterned resist (not shown) as mask to remove part of the gate material layer 54 and part of the gate dielectric layer 52 through single or multiple etching processes. After stripping the patterned resist, a first gate structure 14 and a second gate structure 16 each composed of a patterned gate dielectric layer 52 and a patterned material layer 54 are formed on the substrate 12. Preferably, the gate pattern 18 is disposed on the STI 40 and the first gate structure 14, the second gate structure 16, and the gate pattern 18 connecting the two gate structures 14, 16 are formed in unity and constitute a ring-shaped pattern altogether.

In this embodiment, it would also be desirable to use the salicide block (SAB) 56, the first gate structure 14, and the second gate structure 16 to define the position of silicide layers and the aforementioned source regions and drain regions. For instance, it would be desirable to first form the SAB 56 on part of the top surface and sidewalls of the first gate structure 14 and the second gate structure 16 and the surface of the substrate 12, conduct an ion implant process by using the SAB 56 as mask to form the first drain region 20, the first source region 28, and the second drain region 24 in the second semiconductor layer 50, and then conduct a salicide process by using the same SAB 56 as mask to form silicides on surfaces not covered by the SAB 56, including surfaces on the first drain region 20, the first gate structure 14, the first source region 28, the second gate structure 16, and the second drain region 24.

Preferably, the semiconductor device further includes an interlayer dielectric (ILD) layer (not shown) disposed on the substrate 12 to cover the first gate structure 14 and the second gate structure 16 and a plurality of contact plugs 38 disposed in the ILD layer to electrically connect the first drain region 20, the first source region 28, and the second drain region 24. The formation of the contact plugs 38 could be accomplished by first forming an ILD layer (not shown) on the substrate 12, and then conduct a pattern transfer or photo-etching process by using a patterned mask (not shown) as mask to remove part of the ILD layer adjacent to the first gate structure 14 and the second gate structure 16 for forming contact holes (not shown) exposing the first drain region 20, the first source region 28, and the second drain region 24 underneath. Next, metals including a barrier layer selected from the group consisting of Ti, TiN, Ta, and TaN and a low resistance metal layer selected from the group consisting of W, Cu, Al, TiAl, and CoWP are deposited into the contact holes, and a planarizing process such as CMP is conducted to remove part of aforementioned barrier layer and low resistance metal layer for forming contact plugs 38 electrically connecting the first drain region 20, the first source region 28, and the second drain region 24. Next, a metal interconnective process is conducted to form inter-metal dielectric (IMD) layer (not shown) on the ILD layer and metal interconnections 58 connected to each of the contact plugs 38.

Overall, the present invention provides a novel LDMOS device by first disposing the LDMOS device on a SOI substrate, in which doped regions or body implant regions having conductive type opposite from the source region and drain region are disposed under part of the gate structures and the body implant regions are also disposed extending along the same direction as the gate structures.

Preferably, the present invention could use the presence of the body implant regions to increase finger widths of the transistor and lower gate to body capacitance thereby improving the performance of the device.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

1. A semiconductor device, comprising: a first gate structure on a substrate; a first drain region having a first conductive type adjacent to one side of the first gate structure; a source region having the first conductive type adjacent to another side of the first gate structure, wherein bottom surfaces of the source region and the first drain region are coplanar; a second gate structure on the substrate, wherein the source region is between the first gate structure and the second gate structure; and a first body implant region having a second conductive type under part of the first gate structure and contacting the source region directly.
 2. The semiconductor device of claim 1, further comprising a first drift region having the first conductive type under part of the first gate structure and extended to the first drain region.
 3. The semiconductor device of claim 1, wherein the bottom surfaces of the first drain region and the first body implant region are coplanar.
 4. The semiconductor device of claim 1, wherein an edge of the first body implant region is aligned with an edge of the first gate structure.
 5. The semiconductor device of claim 1, wherein the substrate comprises: a first semiconductor layer; an insulating layer on the first semiconductor layer; and a second semiconductor layer on the insulating layer.
 6. The semiconductor device of claim 5, further comprising: a second gate structure on the substrate, wherein the source region is between the first gate structure and the second gate structure; a second drain region having the first conductive type adjacent to one side of the second gate structure; and a second body implant region having the second conductive type under part of the second gate structure.
 7. The semiconductor device of claim 6, further comprising a second drift region having the first conductive type under part of the second gate structure and extended to the second drain region.
 8. The semiconductor device of claim 6, wherein the bottom surfaces of the second drain region and the second body implant region are coplanar.
 9. The semiconductor device of claim 6, wherein an edge of the second body implant region is aligned with an edge of the second gate structure.
 10. The semiconductor device of claim 6, wherein the first drain region, the second drain region, the first body implant region, and the second body implant region are disposed in the second semiconductor layer.
 11. A semiconductor device, comprising: a first gate structure extending along a first direction on a substrate; a first drain region extending along the first direction on one side of the first gate structure; a first source region adjacent to another side of the first gate structure; and a first body implant region extending along the first direction and overlapping part of the first gate structure, wherein a long side of the first body implant region is less than a long side of the first gate structure.
 12. The semiconductor device of claim 11, further comprising: a second gate structure extending along the first direction on the substrate; a second drain region extending along the first direction on one side of the second gate structure; and a second body implant region extending along the first direction and overlapping part of the second gate structure.
 13. The semiconductor device of claim 12, wherein an edge of the second body implant region is aligned with an edge of the second gate structure.
 14. The semiconductor device of claim 11, wherein an edge of the first body implant region is aligned with an edge of the first gate structure.
 15. The semiconductor device of claim 11, further comprising a second source region above the first source region.
 16. The semiconductor device of claim 15, further comprising a first body contact region extending along a second direction between the first source region and the second source region.
 17. The semiconductor device of claim 16, wherein the first body contact region comprises a second conductive type.
 18. The semiconductor device of claim 11, further comprising a third source region below the first source region.
 19. The semiconductor device of claim 18, further comprising a second body contact region extending along a second direction between the first source region and the third source region.
 20. The semiconductor device of claim 19, wherein the first source region comprises a first conductive type and the second body contact region comprises a second conductive type. 